There is only one Qt :-)
PyQt is a Python binding for Qt and still requires Qt libraries (binaries). So, even if you use PyQt you will need to have Qt libraries which you are using.
If I understood you correctly you need your UI on a computer (not Pi), right? This part is simple - just install the latest stable Qt version an start coding :-)
For the other part you can either directly develop on Pi (using Raspbian you can easily install Qt with apt) or you have to cross compile Qt to develop on your PC. You don't have to cross compile everything, just what you need. See https://wiki.qt.io/Raspberry_Pi_Beginners_Guide

@Cleiton-Bueno thanks for your suggestion. I have disabled audio in my kernel completely now. Now I get the message CameraBin warning: "Could not open audio device for recording." which shows, that I really removed audio support.
Unfortunately, this still doesn't solve my basic issue, which is a extremely sluggish video output when the videoRecorder property is enabled in the Camera. That means, the audio encoding was not causing this problem at all.

I think not. It seems to not deeply use the same "gstreamer plugins". I'm also not sure of my answer, but it is the impression i have.
You can maybe try to change some camera parameters from qml code, but not sure you will have the same result (it's look like luminosity problem).

@SGaist
Thanks for you reply. The only way to create what I need - using Android functions directly and I must forgot about crossplatform for my app (if you want to use, for example, hardware acceleration or something).
The code bellow is the main class (java, for use with QAndroidJniObject), that draws camera preview, using hardware:

@Franckynos
Yes, I know video capture is not supported for windows.
But, I fail already, by the simple camera initialisation. :-(
An idears: driver - codecs missing, user right for camera, what can I do to find out what does not work ....
If I can not solve the problem my whole project will break down.

You might post your code or give us a bit more details...you might have your application defined to rotate screen automatically following the actual device orientation.
Otherwise another simple option is to use the orientation sensor to manage the viewfinder orientation :

So is there any magic involved in getting a decent fps? I am aware that this is more related to QtGstreamer and RPi2 forums, but I've got nothing to lose trying here too as i assume others have been here before me.

Ive been having a hard time finding out what kind of element name would work when generating a pipeline, especially since I'm using Gstreamer 0.10, so I'm thinking the cause of the low FPS may be related a mix of the element name, the pipeline properties, and the (Qt)GStreamer version?